ANKARA, April 2 (Reuters) - Turkey's block on access to Twitter violated freedom of expression and individual rights, the constitutional court said on Wednesday, the most significant legal challenge yet to a ban which caused public uproar and international condemnation.

Turkey's telecoms authority TIB blocked access to Twitter on March 21 after Prime Minister Tayyip Erdogan said he would "root out" the network, following a stream of anonymously posted audio tapes purporting to expose corruption in his inner circle days ahead of nationwide elections.

The constitutional court said it had sent its verdict to the TIB and the Transport Ministry, which also has responsibility for communications. It was not immediately clear whether the ruling would lead to a lifting of the block.

The court received several individual applications challenging the ban, including from a main opposition CHP party deputy and a prominent legal academic.

"If there is anyone who believes there is rule of law and human rights in this country, TIB must execute the court verdict and lift the ban on Twitter," the academic, Kerem Altiparmak, said on his Twitter account.

Erdogan's critics saw the ban as the latest in a series of authoritarian measures to crush a corruption scandal which had grown into one of the biggest challenges of his 11-year rule.

Tech-savvy Turks quickly found workarounds, with Internet analysts reporting a surge in tweets since the ban was imposed, but the issue has become a tug-of-war between Erdogan's administration and the San Francisco-based microblogging site, which has also challenged the move.

Erdogan and his Islamist-rooted AK Party emerged triumphant from municipal elections on Sunday which had become a referendum on his rule.

His party kept control of the two biggest cities, the financial hub of Istanbul, and the capital, Ankara, and increased its share of the national vote. The opposition has contested some of the results, including in Ankara, which saw a close race.

The Supreme Electoral Board (YSK) has yet to announce the final, official results, saying it will consider all the challenges before doing so. Thousands protested outside its offices in Ankara on Tuesday, demanding a recount. (Reporting by Humeyra Pamuk; Editing by Nick Tattersall and Sonya Hepinstall)

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